Method of producing bifocal lenses.



C. W. CONN ER. METHOD OF PRODUCING BIFOOAL LENSES.

APPLIOATION FILED APRJM, 1903.

Patented June 22, 1909.

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ammhfoz Charles W. Conner awe M121 G. W. GONNER.

METHOD OF PRODUCING BIIOGAL LENSES.

APPLICATION rILnn APR. 21, 1903.

925,802. Patented June 22, 1909.

s sums-sum 2.

3141x214? Charles W. Conner 0. W. GONNER. METHOD or rnonncme BIIOGAL LENSES.

APPLICATION FILED APR. 21, 1903.

T NH 04% 2 s un Ju as m a P H k- 3141x1110; I Charles W. Conner CHARLES W. OONNER, OF INDIANAPOLIS, INDIANA.-

METHOD OF PRODUCING BIFOCAL LENSES.

Specification of Letters Patent.

Patented June 22, 1909.

Application filed April 21, 1903. Serial No. 153,697.

ously or in succession, as hereinafter described. In order that my process may be thoroughly understood, the accompanying drawings illustrate apparatus by means of which the process may be performed, and also illustrate several forms of the result of my process.

Figure 1 is an elevation of one form of my improved grinding wheel together with an apparatus for using the same. Fig. 2 a plan thereof, Fig. 3 a vertical section of the apparatus for finishin one of the surfaces, Fig. 4 a plan thereo Fig. 5 is a view showing a transverse section of a crystal provided on one face with a concave surface and an internal plain surface; a vertical section of a lens cut from the crystal; and a partial elevation of a grinding element for producing the crystal; Fig. 6 is a view showing a transverse section of a crystal provided with a concave surface of one dioptric and an internal surface of a different dioptric; a vertical section of a lens cut from the crystal; and a partial elevation of a grinding element for producing the crystal; Fig. 7 a transverse section of a crystal provided on one face with a'concave portion and an intermediate convex portion; a vertical section of a lens cut from the crystal; and a partial elevation of a grinding element for producing the crystal; Fig. 8 a transverse section provided on one face with a convex portion and an intermediate plain ortion; a vertical section of a lens cut from t e crystal; and a partial elevation of a grinding element for producing the crystal; Fig. 9 is a section with a convex portion and an intermediate convex portion of different dioptrics; a vertical section of a lens cut from the crystal; and a partial elevation of a grinding element for producing the crystal. Fig. 10 is a diagram of the lens shown in Fig. 6. Fig. 11 is an elevation of a grinding wheel in which the intermediate portion is sufiicientliy depressed so that it will not serve as a grin ing surface.-

In the Figs. 1 to 4 inclusive 15 indicates a grinding wheel the intermediate peripheral portion 16 of which is parallel with the axis of rotation while the edge portions 17 17 are convex. Wheel 15 is mounted upon the aror 18 and rotated by means of a ulley 19. Mounted above wheel 15, preferab y but not necessarily, at right angles to arbor 18 is a lens rotating arbor 20 journaled in a suitable bracket 21 which is adjustable along a line substantially parallel with the axis of arbor 18 by any suitable means such .as an adj usting screw 22. Arbor 20 is rotated, preferably at a considerably hi her speed than arbor 18 by means of a pifiley 23 and belt 24 which belt passes around idlers 25 and a driving Wheel 26 carried by arbor 18. Ar-

the bearing of bracket 21 and provided with a pin 28 projecting through a ba onet slot 29.

In operationthe lower end 0 arbor 20 is adapted to engage and rotate the lens holding head 30 to which crystal 31 is attached in the usual manner. The crystal 31 may preferably be roughed out, so as to partially conform with the curvature of the grinding surfaces 17, by the ordinary grinding means which need not be here described. After the head 30 together with its attached crystal 31 has been connected to arbor 20 it is held in engagement with the periphery of the grinding wheel 15 by spring 27 and the parts then rotated, the grinding wheel upon its arbor 18, and the crystal 31 upon the axis of arbor 20. The grinding surface 16 operates to produce a central lens surface concentric with the arbor 20 and the grinding surfaces grinding surface 16.

17, 17 simultaneously operate to produce a lens surface concentric with arbor 20 and surrounding the lens surface. produced by the If desired, the two lens surfaces may be ground and finished by the same or similar wheels but in practice I find that this may result in an imperfect central lens surface for the reason that slight irregularities in the surface 16, especially in a line directly beneath or very closely beneath the axis of arbor 20, may possibly produce concentric ridges and l1ollows in the lens surface. For that reason after the crystal 31 has been roughed out by the wheel such as shown in Fig. l, where the surfaces 15 and 17, 17 have substantially the proper dioptrics for the two desired surfaces, I remove said wheel and substitute therefor a wheel such as that shown in Fig. 11 where the intermediate grinding surface is removed, as at b, and grinding is continued until a slight surplus of-mate'rial is left in the center of the crystal as shown in- Fig. 3. The external surface is finished with a wheel similar to the wheel shown in Fig. 11, or by any other desired means, and the crystal is then transferred to the rotating head 32 shown in Fig. 3 and there rotated in conjunction with a grinding plate 33 the under face of" which has been given, the proper dioptric curve desired for the central surface-and the surplus material of the center of the crystal is then reduced by this grinder until the line of junction between --the central surface and the surrounding surface is made practically invisible. 'I-he grind ing plate 33 is of less diameter than the lens surface which it is to grind and finish so that, as it is -moved transversely of the crystal across its center by the arm 34 it will be rotated upon the pin 35 as an axis, by reason of the rotation of the crystal 31 by head 32.

In Fig. 5 I have shown a portion of the periphery of a grinding wheel having a pair of separated surfaces 40 which are of the same dioptric and an intermediate grinding surface 41 which is parallel with the axis of rotation. Such a wheel will produce a lens such as shown in Fig. 5 with a flat central circular surface 41. The finished eye-glass lens is also shown in the same figure, a portion of the crystal having been removed so as to bring the surface41 to one edge of the finished lens.

I "In Fig. 6 the surfaces 42, 42- are of a plus dioptric which is greater than the plus diop trio of the intermediate surface 43. This wheel will produce the lens shown with a .minus central surface 43' and a surrounding minus surface 42 of smaller d optric.

Iii Fig. 7 the grinding surfaces 44, 44 are plus, while the intermediate surface 45 is a minus dioptric and consequently the lens produced has a central plus surface 45 and a surrounding minus surface 44.

In Fig. 8 the minus grinding surfaces 46, 46 have a plain surface 47 interposed and this will produce a lens having a central flat circular portion 47 and a surrounding plus surface 46.

In Fig. 9 the grindingsurfaces 48, 48 are minus and the intermediate grinding surface 49 minus of a greater dioptric thus producing a lens having an intermediate plus surface 49, and a surrounding plus surface 48.

In'Fig. 10 I have shown a section of the eye-glass lens illustrated in Fig. 6 and have further shown that the radius a is common to both of ,the lens surfaces 42 and 43'.

It will be readily understood that, if desired, one of the grinding surfaces 17, 17

may be omitted, or if desired a single grinding surface off-set with relation to the arbor 20 may be used for producing the external or surrounding lens surface but both of these changes would probably prove to be.

which appears to be essential for the production of an accurate lens.

It is to be understood that the side of the crystal opposite that upon which the two surfaces of different dioptrics have been formed may be, and usually will be, given any desired dioptric conformation in any desired manner.

After the crystal has been provided on one face with the two surfaces and the opposite face reduced to the desired conformation an eye-glass or spectacledens is produced by removing a portion of the outer or surrounding surface so that the central surface will then he at the lower edge of the finished lens. It is thus possible to produce from a' single crystal av bifocal lens with the near vision portion properly positioned at the lower edge.

I claim as my invention.

1. The process of makin a bifocal lens from one piece of glass, inc uding as a step therein the simultaneous generation of two concentric siherically disposed visual surfaces of di erent dioptrics upon one-face of the piece of glass.

2. The process of making a-bifocal lens from one piece of glass, which process conas desired, and third in removin a ortion this 18th day of April, A. D. one thousand of said piece of glass to give it t e onn of nine hundred and three.

a finished lens and so that the inner visual surface will lie near one edge of the finished CHARLES OONNER' lens. Witnesses In witness whereof, I, have hereunto set ARTHUR M. H001),

my hand and seal at Indianapolis, Indiana, JAMES A. WALSH. 

